We're barely halfway through August, so I can't bring myself to type the other A word. You know the one I mean. Mists and mellow fruitfulness. Winter seemed to end only about three weeks ago, so I am not in any more of a hurry to say goodbye to this summer than you are. But in fashion, there is no point pretending that summer's trends are anything but old news.

Let's call it the new season. Essentially, it starts on the day after you get back from your big summer holiday, or last summer festival/wedding/jaunt, and dust yourself down and give yourself a back-to-business talking to. Silly season is over.

For any new season you can start with the colours, or the silhouette. The new silhouette is more of a game changer, but it is also more of a commitment. It means turning your back on the blowsiness of summer – and no one wants that just yet.

Let's ease our way into the new season with purple. Purple was anointed the de facto colour of the season once Christopher Kane and Prada had both shown purple clothes, on purple-carpeted catwalks. Specifically, a shade that will be instantly summoned to mind for readers of a certain age by the name Silk Cut Purple.

The catwalk mood for this autumn can be summarised as Pretty Gothic. It is an unfleshy season, and slightly sombre. It is also quite grown up, the conversational kitten prints and jokey neons of last winter having been replaced by elegant florals and dark tones. So it makes sense that we are to graduate out of the school-uniform colours that have dominated most recent autumn/winter seasons – navy and grey, particularly – into purple, which as everyone knows is the official shade of the sixth form common room. Purple is a transitional shade, not childish, but not sophisticated.

The perfect colour, then, to tide us over until the new season truly kicks in, while holding on to the spirit of summer. Match your trousers to your Ribena ice lolly, and don't mention the A word.